一些js小技巧

const params = new URLSearchParams(location.search); // location.search = '?key=dd&value=kk'
params.has('key'); // true
params.get('value'); // kk

const num1 = ~~2.3;
const num2 = 2.3 | 0;
const num3 = 2.3 >> 0;

const a = d && 1; // 满足条件赋值：取假运算，从左到右依次判断，遇到假值返回假值，后面不再执行，否则返回最后一个真值
const b = d || 1; // 默认赋值：取真运算，从左到右依次判断，遇到真值返回真值，后面不再执行，否则返回最后一个假值
const c = !d; // 取假赋值：单个表达式转换为true则返回false，否则返回true

const obj = {};
const flag = !Object.keys(obj).length; // true

const flagA = true; // 条件A
const flagB = false; // 条件B
(flagA || flagB) && Func(); // 满足A或B时执行
(flagA || !flagB) && Func(); // 满足A或不满足B时执行
flagA && flagB && Func(); // 同时满足A和B时执行
flagA && !flagB && Func(); // 满足A且不满足B时执行

const arr = [1, 2, 3];
const _arr = [...arr]; // [1, 2, 3]

const arr1 = [1, 2, 3];
const arr2 = [4, 5, 6];
const arr = [...arr1, ...arr2]; // [1, 2, 3, 4, 5, 6]

const arr = [...new Set([1, 2, 1, 4, 6, null, null])]; // [1, 2 ,4, 6, null]

const arr = [undefined, null, "", 0, false, NaN, 1, 2].filter(Boolean); // [1, 2]

const arr = [0, 1, 1, 2, 2, 2];
const count = arr.reduce((t, v) => {
    t[v] = t[v] ? ++t[v] : 1;
    return t;
}, {});
// count => { 0: 1, 1: 2, 2: 3 }

const people = [
    { name: 'Alice', age: 20 },
    { name: 'Max', age: 21 },
    { name: 'Tom', age: 20 }
]

const groupBy = (objectArr, property) => {
    return objectArr.reduce((acc, obj) => {
        const key = obj[property];
        if (!acc[key]) {
            acc[key] = []
        }
        acc[key].push(obj);
        return acc;
    }, {})
}

const groupedPeople = groupBy(people, 'age');
/* {
    20: [
        { name: 'Max', age: 20 },
        { name: 'Jane', age: 20 }
    ],
    21: [{ name: 'Alice', age: 21 }]
} */

const obj = { a: 0, b: 1, c: 2 }; // 只想拿b和c
const { a, ...rest } = obj; // { b: 1, c: 2 }